Valve seat made of iron-based sintered alloy

Abstract

A valve seat of an iron-based sintered alloy having high wear resistance in a wide temperature range, which can be used in direct injection engines with improved fuel efficiency, low emission and high power, is obtained by limiting the amount of a solid lubricant dispersed in the matrix of the valve seat of an iron-based sintered alloy, and dispersing at least two types of hard particles having different hardnesses in the matrix, thereby providing high strength and self-lubrication, as well as improved wear resistance under no lubrication in a wide temperature range.

1 . A valve seat of an iron-based sintered alloy, in which at least two types of hard particles having different hardnesses, and 0.2-0.8% by mass of a solid lubricant are dispersed. 
     
     
         2 . The valve seat of an iron-based sintered alloy according to  claim 1 , wherein at least two types of said hard particles having different hardnesses comprise 2-8% by mass of first hard particles having an average particle size of 50-150 μtm and Vickers hardness Hv of 800-1200, and 5-15% by mass of second hard particles having an average particle size of 10-150 μm and Vickers hardness Hv of 400-750. 
     
     
         3 . The valve seat of an iron-based sintered alloy according to  claim 1  wherein said first hard particles are made of an Fe-Mo-Si alloy comprising by mass 40-70% of Mo, and 0.1-2.0% of Si, the balance being Fe and inevitable impurities, and said second hard particles are made of an Fe-C-Cr-Mo-V alloy comprising by mass 0.2-0.5% of C, 0.5-5% of Cr, 1-5% of Mo, and 2-5% of V, the balance being Fe and inevitable impurities. 
     
     
         4 . The valve seat of an iron-based sintered alloy according to  claim 1 , wherein matrix, in which at least two types of said hard particles having different hardnesses and said solid lubricant are dispersed, has a composition comprising by mass 0.5-2.5% of C, 0.4-2% of Si, 0.5-5% of Mo, and 1-5% of Ni, the balance being Fe and inevitable impurities. 
     
     
         5 . The valve seat of an iron-based sintered alloy according to  claim 4 , wherein said matrix has a tempered martensite phase and a pearlite phase. 
     
     
         6 . The valve seat of an iron-based sintered alloy according to  claim 1 , wherein said solid lubricant is one or more selected from the group consisting of sulfides and nitrides, having an average particle size of 2-50 μm. 
     
     
         7 . The valve seat of an iron-based sintered alloy according to  claim 2 , wherein said first hard particles are made of an Fe-Mo-Si alloy comprising by mass 40-70% of Mo, and 0.1-2.0% of Si, the balance being Fe and inevitable impurities, and said second hard particles are made of an Fe-C-Cr-Mo-V alloy comprising by mass 0.2-0.5% of C, 0.5-5% of Cr, 1-5% of Mo, and 2-5% of V, the balance being Fe and inevitable impurities. 
     
     
         8 . The valve seat of an iron-based sintered alloy according to  claim 2 , wherein said matrix, in which at least two types of said hard particles having different hardnesses and said solid lubricant are dispersed, has a composition comprising by mass 0.5-2.5% of C, 0.4-2% of Si, 0.5-5% of Mo, and 1-5% of Ni, the balance being Fe and inevitable impurities. 
     
     
         9 . The valve seat of an iron-based sintered alloy according to  claim 2 , wherein said solid lubricant is one or more selected from the group consisting of sulfides and nitrides, having an average particle size of 2-50 μm. 
     
     
         10 . The valve seat of an iron-based sintered alloy according to  claim 3 , wherein said matrix, in which at least two types of said hard particles having different hardnesses and said solid lubricant are dispersed, has a composition comprising by mass 0.5-2.5% of C, 0.4-2% of Si, 0.5-5% of Mo, and 1-5% of Ni, the balance being Fe and inevitable impurities. 
     
     
         11 . The valve seat of an iron-based sintered alloy according to  claim 3 , wherein said solid lubricant is one or more selected from the group consisting of sulfides and nitrides, having an average particle size of 2-50 μm. 
     
     
         12 . The valve seat of an iron-based sintered alloy according to  claim 4 , wherein said solid lubricant is one or more selected from the group consisting of sulfides and nitrides, having an average particle size of 2-50 μm. 
     
     
         13 . The valve seat of an iron-based sintered alloy according to  claim 5 , wherein said solid lubricant is one or more selected from the group consisting of sulfides and nitrides, having an average particle size of 2-50 μm. 
     
     
         14 . The valve seat of an iron-based sintered alloy according to  claim 7 , wherein said matrix, in which at least two types of said hard particles having different hardnesses and said solid lubricant are dispersed, has a composition comprising by mass 0.5-2.5% of C, 0.4-2% of Si, 0.5-5% of Mo, and 1-5% of Ni, the balance being Fe and inevitable impurities. 
     
     
         15 . The valve seat of an iron-based sintered alloy according to  claim 7 , wherein said solid lubricant is one or more selected from the group consisting of sulfides and nitrides, having an average particle size of 2-50 μm. 
     
     
         16 . The valve seat of an iron-based sintered alloy according to  claim 8 , wherein said matrix has a tempered martensite phase and a pearlite phase. 
     
     
         17 . The valve seat of an iron-based sintered alloy according to  claim 10 , wherein said matrix has a tempered martensite phase and a pearlite phase. 
     
     
         18 . The valve seat of an iron-based sintered alloy according to  claim 14 , wherein said matrix has a tempered martensite phase and a pearlite phase. 
     
     
         19 . The valve seat of an iron-based sintered alloy according to  claim 14 , wherein said solid lubricant is one or more selected from the group consisting of sulfides and nitrides, having an average particle size of 2-50 μm. 
     
     
         20 . The valve seat of an iron-based sintered alloy according to  claim 16 , wherein said solid lubricant is one or more selected from the group consisting of sulfides and nitrides, having an average particle size of 2-50 μm.